1. Field
This application relates generally to radiation devices, and more specifically, to treatment and diagnostic radiation devices that generate and/or use tomosynthesis images.
2. Background
Various systems and methods exist to provide radiation therapy treatment of tissue (e.g., tumorous tissue) with high-energy radiation. While some patient conditions require whole body radiation treatments, many forms of radiation treatment benefit from the ability to accurately control the amount, location and distribution of radiation within a patient's body. Such control often includes using a multi-leaf collimator to shape a radiation beam such that the beam has a shape that approximates that of the tumorous region.
Regardless of the form of radiation, many existing radiation treatment procedures require a location of a target region be determined in order to accurately register the target region relative to a radiation source before radiation is applied to the target region. This requires a 3D image of the tumor and surrounding tissue, and is generally accomplished by performing a computed tomography. Computed tomography is an imaging technique that has been widely used in the medical field. In a procedure for computed tomography, an x-ray source and a detector apparatus are positioned on opposite sides of a portion of a patient under examination. The x-ray source generates and directs a x-ray beam towards the patient, while the detector apparatus measures the x-ray absorption at a plurality of transmission paths defined by the x-ray beam during the process. The detector apparatus produces a voltage proportional to the intensity of incident x-rays, and the voltage is read and digitized for subsequent processing in a computer. By taking thousands of readings from multiple angles around the patient, relatively massive amounts of data are thus accumulated. The accumulated data are then analyzed and processed for reconstruction of a matrix (visual or otherwise), which constitutes a depiction of a density function of the bodily section being examined.
A problem associated with registering a target tissue using a CT image is that the CT image may take too long to obtain. In order to perform CT image reconstruction, a sufficient amount of CT image data needs to be generated over a prescribed range of gantry angles. These CT image data take time to generate. Mechanical configuration and/or regulatory rules may limit the rotation rate of a gantry on which the x-ray source and the image detector are mounted. The CT imaging devices that are attached to the gantry of radiation therapy machines have rotation speed that is limited to one rotation per minute. Because of the duration required to generate sufficient CT image data, a patient may not feel comfortable confined within a gantry opening.
In some cases, it may be desirable to continuously monitor a position of a target tissue while a treatment procedure is being performed. For example, a target tissue may move due to physiological movement (e.g., breathing, cardiac motion, coughing, etc.) of a patient. In such cases, it would be desirable to track a movement of the target tissue to ensure that a treatment radiation beam is accurately aimed towards the target tissue. In existing radiation treatment systems, tracking of target tissue does not use CT imaging technique. This is because collecting a sufficient quantity of CT image data for image reconstruction while considering breathing motion may take a long time, and therefore, may not be performed at a fast enough rate, at least not fast enough for real-time tracking of target tissue.